Plasma processing device

ABSTRACT

A plasma processing device that includes a processing chamber which is disposed in a vacuum vessel and is decompressed internally, a sample stage which is disposed in the processing chamber and on which a sample of a process target is disposed and held, and a plasma formation unit which forms plasma using process gas and processes the sample using the plasma, and the plasma processing device includes: a dielectric film which is disposed on a metallic base configuring the sample stage and connected to a ground and includes a film-like electrode supplied with high-frequency power internally; a plurality of elements which are disposed in a space in the base and have a heat generation or cooling function; and a feeding path which supplies power to the plurality of elements, wherein a filter to suppress a high frequency is not provided on the feeding path.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a plasma processing device and a plasmaprocessing method that dispose and hold a sample of a substrate shapesuch as a semiconductor wafer of a process target on a sample stagedisposed in a processing chamber to be disposed in a vacuum vessel andinternally decompressed and process a film layer of a process target ofa film structure having a plurality of film layers including a maskpreviously disposed on a top surface of the sample, using plasma formedin the processing chamber. More particularly, the present inventionrelates to a plasma processing device that transfers heat between asample disposed on a sample stage and the sample stage and processes thesample while adjusting a temperature of the sample.

2. Description of the Related Art

In a process for manufacturing a semiconductor device, a film layer on atop surface of a substrate such as a semiconductor wafer is generallyprocessed using plasma to have a desired shape. For example, a plasmaprocess for processing a film layer of a process target such aspolysilicon on which a resist mask layer is formed in a shape along themask layer by etching a place not covered with a mask is executed.

A plasma processing device typically a vacuum vessel that has aprocessing chamber provided therein, a gas supply device that isconnected to the vacuum vessel and supplies process gas to form plasmaand process a sample to the processing chamber, a vacuum exhaust devicethat includes a vacuum pump such as a turbo-molecular pump and a rotarypump for roughing to exhaust gas or particles in the processing chamberand decompress an inner portion to a predetermined vacuum degree, asample stage in which a wafer to be the sample is disposed on a topsurface on which a dielectric film is disposed, and a plasma generationdevice which supplies an electric field or a magnetic field to excitethe process gas supplied to the processing chamber and generate theplasma to the processing chamber. In a state in which the sampledisposed on the dielectric film configuring the top surface of thesample stage is adsorbed and held on the dielectric film usingelectrostatic force formed by power supplied to an electrode forelectrostatic adsorption in the sample stage, atoms or molecules of theprocess gas supplied to the processing chamber from an introduction portof a shower plate configuring a ceiling surface of the processingchamber and disposed on the processing chamber are excited using theelectric field or the magnetic field formed by the plasma generationdevice and the plasma is formed. Then, a potential difference with apotential of the plasma is formed by a bias potential formed byhigh-frequency power supplied to a metallic electrode disposed in thesample stage, charged particles of the plasma are attracted to a surfaceof a film layer of a process target on the top surface of the sampleaccording to the potential difference to cause the charged particles tocollide with the film layer, a mutual action with reactive particles inthe plasma is accelerated, and an etching process is executed on thefilm layer.

According to a recent demand for improving integration of asemiconductor device, there are a demand for improving minuteprocessing, that is, processing precision and a demand for adjusting atemperature of the surface of the sample during processing, affecting adimension such as a line width of a circuit of the semiconductor deviceafter the processing, with high precision, according to minuteness ofthe line width of the circuit. Meanwhile, recently, it is demanded touse a sample such as a semiconductor wafer having a large diameter tosuppress a manufacturing cost of a semiconductor device element fromincreasing. To adjust the temperature of the sample with high precisionin a plane of a substrate, it is necessary to adjust a distribution ofvalues of the temperature of the substrate surface for each dividedregion in the plane and the temperature in the plane to a predetermineddistribution with high precision. To achieve this, it is thought that aregion of a sample placement surface of the sample stage is divided intoa plurality of regions and the temperature is adjusted variably in eachregion.

An example of the related art is disclosed in JP-2014-150160-A.JP-2014-150160-A discloses that a plurality of heaters disposed atpositions corresponding to a plurality of divided regions of a placementsurface are included in a dielectric film configuring the placementsurface on which a semiconductor wafer of a sample stage is disposed,the heaters disposed in a ring shape on a portion of an outercircumferential side of the placement surface are divided into aplurality of concentric regions, a current control element connected inparallel to each of the concentric portions of the heaters is disposed,a current flowing to the heater is bypassed to adjust an amount ofcurrent flowing to the concentric portion, and temperatures of theplacement surface and the portion of the outer circumferential side ofthe sample with respect to a circumferential direction of the portion ofthe outer circumferential side of the ring shape are adjusted to adesired temperature. In addition, JP-2014-150160-A discloses that powerof a power supply for the heater is consumed at the bypass side suchthat the power becomes constant, the temperature of the sample on theheater is predicted using a temperature sensor disposed in the samplestage located below the heater, and an amount of power supplied to theheater or an amount of heat generation of the heater and the temperatureof the sample are adjusted on the basis of a result predicted by anobserver.

Further, JP-2014-112672-A discloses that a plurality of heater arrays(including a Peltier element) are disposed in a ceramic film in which anelectrode to electrostatically adsorb a sample is disposed, powercontrolled by time average control is supplied to each array, values oftemperatures and a distribution thereof with respect to an in-planedirection on a top surface of the film are adjusted to be suitable for aprocess.

SUMMARY OF THE INVENTION

In the related art, a problem occurs because the following points arenot sufficiently considered.

That is, according to the present inventors, the temperature can beadjusted for each of the regions obtained by dividing the surface of thewafer with respect to the in-plane direction, but a use is limited andobtained performance is limited.

For example, in JP-2014-150160-A, the temperature of the top surface ofthe dielectric film increased or decreased by heating of the heaterdisposed in the dielectric film disposed on the base to be the electrodemade of the metallic member in the sample stage is predicted anddetected using an output from the temperature sensor disposed in thebase below the heater and a heating degree of the heater is adjusted. Inthis configuration, when the number of elements of the temperaturesensors increases, a temperature detection time increases andresponsiveness of control of the temperature is lowered.

In addition, in JP-2014-112672-A, because the high-frequency power isapplied to the base in the sample stage, a shield structure to preventthe high-frequency power from being superposed on the heater arraydisposed in the ceramic film is provided. For this reason, a filterdisposed on a primary side of the heater array is complicated and amanufacturing or maintenance cost increases.

An object of the present invention is to provide a plasma processingdevice that has a simple structure and high responsiveness.

The object is achieved by a plasma processing device that includes aprocessing chamber which is disposed in a vacuum vessel and isdecompressed internally, a sample stage which is disposed in theprocessing chamber and on which a sample of a process target is disposedand held, and a plasma formation unit which forms plasma using processgas and processes the sample using the plasma, and the plasma processingdevice includes: a dielectric film which is disposed on a metallic baseconfiguring the sample stage and connected to a ground and includes afilm-like electrode supplied with high-frequency power internally; aplurality of elements which are disposed in a space in the base and havea heat generation or cooling function; and a feeding path which suppliespower to the plurality of elements, wherein a filter to suppress a highfrequency is not provided on the feeding path.

According to the present invention, high-frequency power and an elementfor temperature adjustment in a sample stage are isolated from eachother and a configuration for feeding the element is simplified. Inaddition, a configuration for sealing inner and outer sides of thesample stage airtightly can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent fromthe following description of embodiments with reference to theaccompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view schematically illustratinga configuration of a plasma processing device according to an embodimentof the present invention;

FIG. 2 is an enlarged horizontal cross-sectional view schematicallyillustrating an arrangement of temperature adjustment arrays of a samplestage of the plasma processing device according to the embodimentillustrated in FIG. 1;

FIGS. 3A and 3B are enlarged cross-sectional views schematicallyillustrating a configuration of the sample stage of the plasmaprocessing device according to the embodiment illustrated in FIG. 1;

FIGS. 4A and 4B are enlarged cross-sectional views schematicallyillustrating a configuration of a sample stage of a plasma processingdevice according to a modification of the embodiment illustrated in FIG.1;

FIG. 5 is a horizontal cross-sectional view schematically illustratingan arrangement of temperature adjustment arrays in the sample stageaccording to the embodiment illustrated in FIG. 2;

FIG. 6 is a diagram schematically illustrating an operation of thetemperature adjustment arrays of the sample stage according to theembodiment illustrated in FIG. 2; and

FIG. 7 is a flowchart illustrating a process for detecting a targettemperature of each temperature adjustment array by a control device inthe plasma processing device according to the embodiment illustrated inFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail below with reference to the accompanying drawings, wherein likereference numerals refer to like parts throughout.

The present invention has a plurality of temperature adjustment arraysnot having a high-frequency cut filter and has a simple feedingstructure.

First Embodiment

Hereinafter, an embodiment of the present invention will be describedusing FIGS. 1 to 3B. FIG. 1 is a longitudinal cross-sectional viewschematically illustrating a configuration of a plasma processing deviceaccording to an embodiment of the present invention. Particularly, inthe plasma processing device according to this embodiment, electroncyclotron resonance (ECR) is induced using an electric field of amicrowave band of a specific frequency and a magnetic field of strengthsuitable for the electric field, plasma is formed, and an etchingprocess is executed on a sample of a substrate shape such as asemiconductor wafer of a process target.

In a plasma processing device 100 according to this embodiment, an outercircumferential end of a dielectric window 103 such as quartztransmitting a microwave is disposed on an upper end of a sidewall of acircular cylindrical shape of a vacuum vessel 101 which has a circularcylindrical shape and of which an upper portion is opened, inner andouter sides of the vacuum vessel 101 are airtightly sealed, and aprocessing chamber 104 to be a space of a circular cylindrical shape,which is internally decompressed and in which plasma is formed, isconfigured. In addition, a vacuum exhaust port 110 communicating withthe processing chamber 104 is disposed on a lower portion of the vacuumvessel 101 and the lower portion of the vacuum vessel 101 is connectedto a vacuum exhaust device (not illustrated in the drawings) including avacuum pump that is disposed below the vacuum vessel 101 with the vacuumexhaust port 110 therebetween.

In a place configuring a ceiling surface of the processing chamber 104below the dielectric window 103 configuring an upper portion of thevacuum vessel 101, a plurality of through-holes through which etchinggas is introduced into the processing chamber 104 are disposed in acenter portion and a shower plate 102 of a cylindrical shape made ofquartz is disposed.

To transmit the electric field to generate the plasma in the processingchamber 104 to the processing chamber 104, a waveguide 105 that isconnected to a center of an upper portion of a circular cylindricalcavity to transmit the electric field and has a circular cross-sectionis disposed on the dielectric window 103, on the vacuum vessel 101. Thewaveguide 105 includes a circular cylindrical portion of which a centeraxis extends in a vertical direction and a rectangular portion of whichone end is connected to an upper end of the circular cylindrical portionand an axis extends in a horizontal direction and which has arectangular cross-section. The electric field propagating through aninner portion is oscillated by a power supply 106 disposed on the otherend of the rectangular portion and is supplied to the rectangularportion.

In this embodiment, a frequency of the electric field for the plasmaformation is not limited in particular. However, in this embodiment, amicrowave of 2.45 GHz is used. On the cavity connected to a lower end ofthe circular cylindrical portion of the waveguide 105 and having adiameter larger than a diameter of the waveguide 105 and equal to adiameter of the processing chamber 104 and at an outer circumferentialside of lateral portions of the cavity and the processing chamber 104,coils 107 to form a magnetic field are disposed to surround the cavityand the processing chamber 104. The electric field that is formed in thepower supply 106, propagates through the waveguide 105, passes throughthe cavity, transmits the dielectric window 103, and is supplied to theprocessing chamber 104 acts mutually with the magnetic field formed bythe coils 107 and supplied to the processing chamber 104 and excitesatoms or molecules of the process gas introduced into the processingchamber 104. Plasma 116 of a high density is generated in the processingchamber 104 by excited particles of the process gas.

A configuration of a sample stage according to an embodiment of thepresent invention will be described using FIGS. 1 to 3B. FIG. 2 is anenlarged horizontal cross-sectional view schematically illustrating anarrangement of temperature adjustment arrays of the sample stage of theplasma processing device according to the embodiment illustrated inFIG. 1. FIGS. 3A and 3B are enlarged cross-sectional views schematicallyillustrating the configuration of the sample stage of the plasmaprocessing device according to the embodiment illustrated in FIG. 1.FIG. 3A illustrates a longitudinal cross-section and FIG. 3B illustratesa horizontal cross-section.

A sample stage 115 of which a top surface faces a bottom surface of thedielectric window 103 or the shower plate 102, a wafer 109 to be asample being disposed on the top surface, is disposed in a lower portionin the processing chamber 104 illustrated in FIG. 1. The sample stage115 has a circular cylindrical shape and the top surface thereof onwhich the wafer 109 is disposed is covered with the dielectric film 111.

Conductive films 220 for electrostatic adsorption that are supplied withdirect-current power and form electrostatic force by a charge betweenthe dielectric film 111 and the wafer 109 are disposed in the dielectricfilm 111. Each of the conductive films 220 according to this embodimenthas a tandem type with a plurality of teeth. However, the individualteeth are inserted between the teeth such that the individual teeth areengaged.

The conductive film 220 of the upper left side of FIG. 1 is electricallyconnected to a direct-current power supply 132 having negative polarityvia a high-frequency filter 125. In addition, the conductive film 220 ofthe upper right side of FIG. 1 is electrically connected to adirect-current power supply 126 having positive polarity via thehigh-frequency filter 125.

In addition, a conductive film 221 is disposed below the conductive film220 in the dielectric film 111, the conductive film 221 and thehigh-frequency power supply 124 are electrically connected via amatching circuit 129, and high-frequency power for bias potentialformation is supplied from a lower side of a center of the wafer 109.The conductive film 221 and the conductive film 220 for an electrostaticchuck to which the high-frequency power is supplied is surrounded with adielectric material made of ceramics such as alumina and yttriaconfiguring the dielectric film 111 and are disposed under gas of theprocessing chamber 104 decompressed to a predetermined vacuum degree.

In this example, the two conductive films 220 are disposed at a positionsymmetric with a center of the wafer 109 having a discoid shape or ashape equal to the discoid shape or an axis passing the center. Thereason is as follows. When if the high-frequency power supplied to theconductive film 221 flows through a feeding position of the conductivefilm 220 on the conductive film 221, a high-frequency electric field maybe generated in the conductive film 220. That is, even though theelectric field by the high-frequency power is generated in theconductive film 220, the two films are disposed symmetric with thecenter of the wafer 109, so that a difference of adsorption strength orperformance is reduced at the left and right sides.

In this embodiment, the reason why the high-frequency power is appliedfrom the center of the wafer 109 is as follows. The gas in theprocessing chamber 104 of the plasma processing device 100 is exhaustedat a position aligned with an axis of a circular cylinder of the samplestage 115, from the vacuum exhaust port 110 in which the axis isdisposed.

The wafer 109 is disposed at a position matched with a center of a waferplacement surface having a circular shape equal to a shape of thedielectric film 111 of an upper portion of the sample stage 115. On atop surface of the wafer 109, distributions of pressures (partialpressures) of the process gas or reaction products and particles of theplasma form a concentric shape around a center axis. As a result of anetching process, a processing shape and performance such as acharacteristic of etching become also a distribution of a concentricshape. For this reason, the electric field of the high-frequency poweris distributed in a concentric shape from the center, the pressuredistribution of particles such as the process gas is corrected with aconcentric shape, and a variation of the distribution of the processingshape of the wafer 109 with respect to a circumferential direction isreduced to be approximately equalized.

In addition, because the sample stage 115 according to this embodimentneeds to cool heat generated by the high-frequency power supplied fromthe direct-current power supplies 126 and 132 and the high-frequencypower supply 124 or the temperature adjustment array 220 disposed in abase 114, a cooling medium flow channel 219 through which the coolingmedium flows is disposed in the base 114. Upper and lower sensors forpins (not illustrated in the drawings) that contact a back surface ofthe wafer 109 with a leading end thereof and ascends or descends thewafer 109 on the dielectric film 111 in a state in which the upper andlower arms hold the wafer 109 are disposed in the base 114. The sensorsmay malfunction in a state in which there is electrical noise.

In addition, the cooling medium flowing through the cooling medium flowchannel may be electrostatically charged in the electric field.Therefore, in this embodiment, as illustrated in the drawings, the base114 is electrically connected to a ground electrode 112. By thisconfiguration, even though an insulating cooling medium such as afluorocarbon cooling medium is not used, a configuration of a pipe tosupply a cooling medium using water or ethylene glycol and circulate thecooling medium can be simplified and an environment load can be reduced.

In this embodiment, the temperature adjustment array 200 disposed in thebase 114 is also disposed in a space surrounded with a member having aground potential, a high-frequency cut filter to suppress high-frequencypower for bias formation from being supplied to a power supply of aprimary side to supply power to the temperature adjustment array 200 canbe omitted, and a configuration of the sample stage 115 including thetemperature adjustment array 200 is simplified.

The wafer 109 carried in the processing chamber 104 is electrostaticallyadsorbed and held on a top surface of the dielectric film 111 by theelectrostatic force formed between the dielectric film 111 and the wafer109 by the direct-current voltage applied from the direct-current powersupplies 126 and 132. In this state, the etching gas is introduced intoa gap between the dielectric window 103 and the shower plate 102 via amass flow controller (not illustrated in the drawings) and diffusesthrough the gap, the gap is filled with the etching gas, and the etchinggas passes through a gas introduction hole to be a through-hole disposedin a center portion of the shower plate 102 and is introduced into theprocessing chamber 104 to be supplied to the sample stage 115 from theupper side.

As described above, the electric field and the magnetic field aresupplied from the waveguide 105 and the coil 107, the process gas isexcited, and the plasma 116 is generated in the processing chamber 104.The high-frequency power is supplied from the high-frequency powersupply 124 connected to the conductive film 221 disposed in thedielectric film 111 of the sample stage 115, charged particles of theplasma 116 are attracted to a surface of a process target film of a filmstructure for a device circuit configured using a plurality of filmlayers including a mask previously formed on the surface of the wafer109, according to a potential difference of a bias potential formed on atop surface of the wafer 109 and the plasma 116, the charged particlescollide with the surface of the film, and the etching process of thecorresponding film layer is executed. The etching gas or the particlesof the reaction products generated by etching are scattered downwardalong a flow in the processing chamber 104, passes through the vacuumexhaust port 110 communicating with the lower portion of the processingchamber 104, are input to an inlet of a vacuum pump (not illustrated inthe drawings), and are exhausted.

In this embodiment, the sample stage 115 is disposed in the processingchamber 104 decompressed to a vacuum degree suitable for the process.Meanwhile, the temperature adjustment array 200 is disposed in themetallic base 114 and an inner side thereof is disposed in a space heldat an atmospheric pressure. The space is formed between a metalliccap-type structure 216 and a metallic discoid cooling plate 217 to beupper and lower members configuring the base 114.

The cap-type structure 216 has at least one recessed portion formed withan opening provided in a bottom surface at an inner side of an outercircumferential wall of a discoid shape, contacts a top surface of aflat shape of the cooling plate 217 with a sealing member such as anO-ring therebetween, in a state in which the plurality of temperatureadjustment arrays 200 are stored in the recessed portion, and isconnected to the cooling plate 217. In addition, because the cap-typestructure 216 is connected to the ground electrode 112 and has a groundpotential at all times, the cap-type structure 216 has a constantpotential and prevents a high-frequency electric field from beingtransmitted to the space in the recessed portion. For this reason, inthis embodiment, a complicated high-frequency cut filter is not used ona feeding path of the temperature adjustment arrays 200 and the plasmaprocessing device 100 including the sample stage 115 according to thisembodiment in which the plurality of temperature adjustment arrays 200are disposed can be simplified.

In addition, the thickness between the wafer 109 and the temperatureadjustment array 200 is preferably decreased to the thickness capable ofholding structural strength, to realize heat transfer between each ofthe plurality of temperature adjustment arrays 200 and the wafer 109with high precision, such that the recessed portion of the cap-typestructure 216 is under the atmospheric pressure and a temperature of thetop surface of the wafer 109 becomes a predetermined value. To satisfyconflicting requests, in this embodiment, a plurality of protrusions aredisposed in the recessed portion of the cap-type structure 216. Leadingends of the protrusions are disposed at positions corresponding toopenings of the through-holes disposed in a contact surface of thecooling plate 217 connected to lower ends of the protrusions with thecap-type structure 216.

In a state in which the cap-type structure 216 and the cooling plate 217contact each other, screws or bolts 212 are inserted into female screwsthrough the through-holes from the lower portion of the cooling plate217 and both the cap-type structure 216 and the cooling plate 217 arefastened. Because the O-ring to airtightly seal inner and outer sides isinterposed and held in a portion of an outer circumferential side of abottom surface of a sidewall of a circular cylinder of the cap-typestructure 216 having a circular cylindrical shape or a discoid shape,the leading ends of the protrusions in the recessed portion of thecap-type structure 216 and the surface of the portion of the outercircumferential side of the bottom surface of the cap-type structure 216are disposed on the same plane 213 to contact the top surface of thecooling plate 217 under the same pressure.

In a state in which the cap-type structure 216 and the cooling plate 217are connected and fastened, the temperature adjustment arrays 200 andheat insulating placement stages 201 disposed below the temperatureadjustment arrays 200, having elasticity, and made of an insulatingmaterial are interposed by the top surface of the inner wall of therecessed portion of the cap-type structure 216 and the top surface ofthe cooling plate 217 in a space surrounded with the inner wall of therecessed portion of the cap-type structure 216 and the top surface ofthe cooling plate 217 and positions thereof are fixed. In this state,the heat insulating placement stage 201 is compressed in a verticaldirection and is deformed. In this state, repulsive force generated whenthe heat insulating placement stage 201 is compressed and deformed in avertical direction pushes the temperature adjustment array 200 disposedon the heat insulating placement stage 201 to the top surface of theinner wall of the cap-type structure 216, contacts the temperatureadjustment array 200 with the cap-type structure 216, and forms apressure of a contact in which a heat transfer amount sufficient foradjusting the temperature of the top surface of the cap-type structure216 or the top surface of the sample stage 115 with high precision bythe temperature adjustment array 200 is obtained.

To realize the above configuration, the bottom surface of the cap-typestructure 216 according to this embodiment is formed by polishing,including a sealing surface of the portion of the outer circumferentialside, after the recessed portion and the plurality of protrusions areformed. In a state in which both the cap-type structure 216 and thecooling plate 217 are fastened by the bolts 212, flatness of aconnection surface is maintained and the top surface of the cap-typestructure 216 on which the dielectric film 111 is disposed is flattened,so that a variation of a distance between each temperature adjustmentarray 200 having a temperature sensor 218 and the wafer 109 on eachtemperature adjustment array 200 is reduced. Thereby, a variation ofgradients of a temperature of each temperature adjustment array 200 anda temperature of a corresponding place of the wafer 109 disposed on thetemperature adjustment array 200 is suppressed, a deviation of thermalconduction or adsorption performance of the wafer 109 with respect to anin-plane direction is suppressed, and the temperature can be adjustedwith high precision. In addition, because the recessed portion is undera pressure equal to the atmospheric pressure, a sealing structure of afeeding portion of each temperature adjustment array 200 is unnecessaryor simplified and a cost of the device is reduced.

Because the temperature adjustment array 200 to adjust the heat or theheat generation amount is disposed in the internal space of the memberhaving the ground potential, it is not necessary to use a fluorocarboncooling medium to be a cooling medium of an insulation system tosuppress the high-frequency power from leaking, water or ethylene glycolhaving conductivity can be used as the cooling medium, a load of anenvironment in which the device is disposed is reduced, and a pipemember of a circulation device of the cooling medium can be simplified.

As illustrated in FIGS. 3A and 3B, a sealing portion 222 that contactsthe cooling plate 217 with an O-ring 215 disposed at the outercircumferential side of the bottom surface of the cap-type circularcylindrical structure 216 therebetween is disposed to surround therecessed portion and the plurality of temperature adjustment arrays 200in the recessed portion. The heat of the cap-type structure 216 istransmitted to the cooling medium of the cooling medium flow channel 219of the cooling plate 217 via the sealing portion 222 and the temperatureof the outer circumferential portion of the cap-type structure 216 maydeviate from the predetermined value. In this embodiment, a heatinsulating layer 214 having a high heat insulating material is disposedin a ring shape at the outside of the temperature adjustment array 200in the recessed portion of the cap-type structure 216, transfer of theheat at a corresponding outer circumferential portion is suppressed, andthe temperature of the wafer 109 is suppressed from deviating from thepredetermined value. Even when the temperature cannot be sufficientlysuppressed from deviating from the predetermined value at the portion ofthe outer circumferential side of the wafer 109 despite the heatinsulating layer 214 is used, a heating mechanism such as a heater maybe disposed instead of the heat insulating layer 214 or in the heatinsulating layer 214 and the temperature of the region of the outercircumferential side of the wafer 109 may be adjusted.

As illustrated in FIG. 2, in this embodiment, the plurality oftemperature adjustment arrays 200 are disposed in a concentric shape ata plurality of radius positions around a center axis of the cap-typestructure 216 of the cylindrical shape in a direction vertical to aplane of paper in FIG. 2 and the plurality of temperature adjustmentarrays 200 at the individual radius positions are electrically connectedto each other. As illustrated in FIG. 2, because the feeding path isdisposed on the center of the sample stage 115 according to thisembodiment to supply the high-frequency power for the bias formation tothe center of the circular conductive film 221 in the dielectric film111, the temperature adjustment array 200 is disposed on a centerportion of the recessed portion of the cap-type structure 216.

Each of the plurality of temperature adjustment arrays 200 according tothis embodiment has a Peltier element to be fed and a temperaturedifference is generated between two surfaces of the Peltier element, sothat a temperature of a member connected to one surface can be increasedor decreased. In addition, each of the plurality of temperatureadjustment arrays 200 according to this embodiment is provided with acurrent bypass relay 206 (only one current bypass relay is illustratedin FIG. 2) and can adjust each temperature to a desired valueindividually. In this embodiment, in an aggregation of the plurality oftemperature adjustment arrays 200 disposed in a circumferentialdirection at the individual radius positions, the two temperatureadjustment arrays adjacent to each other in the circumferentialdirection are electrically connected to each other. The two temperatureadjustment arrays of both ends of the aggregation of the plurality oftemperature adjustment arrays 200 are connected to a constant currentpower supply 207 via positive and negative terminal electrodes of apolarity switch 208 to send a signal to switch between a Peltier modeand a heater mode.

In FIG. 2, connection with the constant current power supply 207 and thepolarity switch 208 with respect to only the aggregation of thetemperature adjustment arrays 200 at the radius positions of theoutermost circumference is illustrated. However, at least oneaggregation disposed at radius positions of an inner circumferentialside is connected to a pair of the constant current power supply 207 andthe polarity switch 208. In this embodiment, for each aggregation of thetemperature adjustment arrays 200 disposed to correspond to apredetermined concentric region of the wafer 109 of the upper side withrespect to the circumferential direction at each radius position,operation switching between heating and cooling of each aggregation andheating and cooling amounts are adjusted by an operation of a pair ofthe constant current power supply 207 and the polarity switch 208.

As such, in this embodiment, in the plurality of aggregations of thetemperature adjustment arrays 200 disposed in the circumferentialdirection in the regions corresponding to the plurality of radiuspositions, the temperature adjustment arrays adjacent to each other areconnected in series. As a result, to correspond to a distribution of aconcentric shape of a density of particles of gas or radical in theprocessing chamber 104 on the wafer 109, a distribution of thetemperature of the top surface of the wafer 109 or the dielectric film111 can be set differently in the radial direction and correction can beperformed to suppress a change in the circumferential direction. Forthis function, the polarity of the Peltier element of the temperatureadjustment array 200 can be set equally in the circumferential directionfor every aggregation and can be set differently in the aggregation ofthe temperature adjustment arrays at the different radius positions.

In this embodiment, a space surrounded and divided by the recessedportion of the cap-type structure 216 and the cooling plate 217 in astate in which the base 114 is configured is under a pressure equal tothe atmospheric pressure, air is sealed in the space, and moisture isincluded in the space. For this reason, in FIGS. 3A and 3B, when thetemperature adjustment array 200 is driven in the Peltier mode and isused in a cooling operation, condensation may be formed in the space andwater droplets may cause a short circuit in the Peltier element of thetemperature adjustment array, and a malfunction or a failure may occur.To suppress the condensation, in this embodiment, air heated at apredetermined temperature and having reduced relative humidity or gassuch as rare gas is introduced into the recessed portion from anintroduction port 210 and the air is exhausted from the space through anexhaust port 211 for circulation.

In addition, each temperature adjustment array 200 according to thisembodiment has the temperature sensor 218 and a signal output from thetemperature sensor disposed in each temperature adjustment array 200 istransmitted to a control device not illustrated in the drawings. Acommand signal calculated on the basis of a value showing a temperaturedetected from the signal in the control device is transmitted to each ofthe previous temperature adjustment arrays 200 or the plurality oftemperature adjustment arrays 200 including other temperature adjustmentarray 200 and drive of the Peltier element or the heater element isadjusted.

The adjustment of the temperature adjustment array 200 is also performedby bypassing a current by the non-polar bypass relay 206 connected toeach temperature adjustment array 200. The reason why the bypass relay206 according to this embodiment is the non-polar bypass relay is tobypass the current without depending on the mode, because thetemperature adjustment array 200 switches between the Peltier mode andthe heater mode by switching of a direction (polarity) of the current.

In addition, the bypass relay 206 needs to have a value of resistancesufficient lower than resistance of the temperature adjustment array 200to improve bypass performance of the bypass relay 206. According to anexamination of the present inventors, the bypass relay 206 can be usedpracticably by setting a resistance value equal to or smaller than about⅕ of the resistance value of the temperature adjustment array 200.

A modification of the electrode structure according to the embodiment ofthe present invention will be described using FIGS. 4A and 4B. FIGS. 4Aand 4B are enlarged cross-sectional views schematically illustrating aconfiguration of a sample stage of a plasma processing device accordingto a modification of the embodiment illustrated in FIG. 1. FIG. 4Aillustrates a longitudinal cross-section and FIG. 4B illustrates ahorizontal cross-section.

As illustrated in FIGS. 4A and 4B, in this example, a pair of eachtemperature adjustment array 300 and each temperature sensor 318 isdisposed vertically. In a state in which the cap-type structure 216 andthe cooling plate 217 are connected and fastened and the base 114 isconfigured, the temperature sensor 318 is interposed by the temperatureadjustment array 300 below the temperature sensor 318 and a top surfaceof an inner wall of a recessed portion of the cap-type structure 216 onthe temperature sensor 318 and contacts both the temperature adjustmentarray 300 and the cap-type structure 216. In this configuration, acontrol device not illustrated in the drawings detects a temperature onthe basis of a signal output from each temperature sensor 318 andadjusts drive of elements of each temperature adjustment array 300 orthe plurality of temperature adjustment arrays 300 by bypassing acurrent using a non-polar bypass relay 306.

In this example, each of the temperature sensor 318 and the temperatureadjustment array 300 is configured using a film-like member. Thetemperature sensor 318 has a film-like structure 301 having the samethickness as the thickness of an element disposed around an element todetect the temperature and reduces a deviation or a variation of heattransmitted to the temperature sensor 318 interposed between the innerwall of the recessed portion of the cap-type structure 216 and thetemperature adjustment array 300, with respect to an in-plane directionof a film.

The temperature adjustment array 300 according to this example isoperated in only a motor mode. For this reason, because a direction of acurrent flowing to each element during an operation of the plasmaprocessing device 100 does not change, a polar bypass relay can be usedas the bypass relay. In addition, according to the examination of thepresent inventors, the bypass relay can be used practicably by setting aresistance value equal to or smaller than about ⅕ of the resistancevalue of the temperature adjustment array 200.

To obtain heat conduction sufficient for realizing temperatureadjustment with desired precision by contacting the temperatureadjustment array 300 with the top surface of the inner wall of therecessed portion of the cap-type structure 216 under a sufficientpressure, a heat insulating structure 311 made of an elastic member isdisposed between the temperature adjustment array 300 and the topsurface of the cooling plate 217 in a space in the recessed portion. Inthis configuration, in a state in which the cap-type structure 216 andthe cooling plate 217 are connected and fastened, the temperatureadjustment array 300, the temperature sensor 318 disposed on thetemperature adjustment array 300, and the heat insulating structure 311are interposed between the cap-type structure 216 and the cooling plate217 and contact each other. The temperature adjustment array 300 and thetemperature sensor 318 disposed on the temperature adjustment array 300are pushed from the heat insulating structure 311 to the top surface ofthe inner wall of the recessed portion of the cap-type structure 216 byrepulsive force generated when the heat insulating structure 311 havingthe elasticity is compressed and deformed or pressing force transmittedfrom the cooling plate 217 and a sufficient contact pressure isgenerated between the temperature sensor 318 and the cap-type structure216.

The heat insulating structure 311 has a shape equal to a shape of arectangular parallelepiped. However, the shape of the heat insulatingstructure 311 is not limited thereto. Because the heat insulatingstructure 311 has a heat insulating property, the heat insulatingstructure 311 can suppress the heat generated by the heater of thetemperature adjustment array 300 from being transmitted to the coolingplate 217 and adjust the temperature of the top surface of the cap-typestructure 216 with high precision. To realize the heat transfer ortemperature adjustment, a heat transfer rate of the heat insulatingstructure 311 according to this example is preferably 5 W/mK or less.

Control of an operation of the temperature adjustment array in theembodiment will be described using FIG. 5. FIG. 5 is a horizontalcross-sectional view schematically illustrating an arrangement oftemperature adjustment arrays in the sample stage according to theembodiment illustrated in FIG. 2. In FIG. 5, the temperature adjustmentarrays 200 disposed in the cap-type structure 216 of the sample stage115 having a circular cross-section are disposed radially in a radialdirection from the center at an interval of the same angles in acircumferential direction at three radius positions and configure threeaggregations electrically connected in series.

Numbers are assigned to the temperature adjustment arrays 200sequentially from one end of a row of arrays to the other end in theaggregation of the temperature adjustment arrays 200 of the innermostcircumference. If numbers are assigned to all of the temperatureadjustment arrays 200 (1 to 4 in this example) of the innermostcircumference, numbers are assigned to all of the temperature adjustmentarrays 200 (in this example, 5 to 12) sequentially from one end of a rowof arrays to the other end at first outer circumference side, and thisprocess is repeated until numbers are assigned to all of the temperatureadjustment arrays 200 in the aggregation of the temperature adjustmentarrays 200 of outermost circumference. As a result, numbers are assignedto all of the temperature adjustment arrays 200 of the sample stage 115.

A process for adjusting the temperature of the top surface of the samplestage 115 or the dielectric film 111 by adjusting an operation of eachof the temperature adjustment arrays 200 to which numbers 1 to h areassigned will be described below. In this configuration, if anadjustment target temperature is set, the operation of each temperatureadjustment array 200 is executed by feedback control such as PID controlcontrolled according to a command signal sent by the control device notillustrated in the drawings, which receives the signal output from thetemperature sensor 218.

Hereinafter, detection of a target temperature (sensor feedbacktemperature) Tn of an (n-th) element having any number n will bedescribed. A temperature Twn in a place of the top surface of the wafer109 disposed on the n-th element of the temperature adjustment array 200is calculated from data showing a value of a critical dimension (CD)representing a shape of the wafer 109 as follows.

A correlation of the value of the CD and the temperature is 1:1 and thetarget temperature is calculated from a correlation coefficient and thevalue of the CD and is set. That is, an influence constant λkn from then-th element to a k-th element is determined according to a distancebetween the temperature adjustment arrays and positions thereof. Forexample, in the case in which the temperature of the k-th temperatureadjustment array 200 rises by 10% after a predetermined time when thetemperature of the n-th temperature adjustment array is set by 1° C. byprevious experiments, the influence constant λkn is determined as 0.1.When the influence constant is determined uniquely, it is thought thatthe temperature of the n-th temperature adjustment array 200 and thetemperatures of the surrounding temperature adjustment arrays 200 are ina proportional relation.

In addition, the temperature of the wafer 109 is increased by the heatinput from the plasma 116. An amount of heat input from the plasma 116and the magnitude of the high-frequency power for the bias formation arein a predetermined correlation and the amount of heat input from theplasma 116 is calculated by applying a correlation coefficient K to themagnitude of the high-frequency power for the bias formation. This isbecause it is necessary to relatively decrease the temperature of thetop surface of any temperature adjustment array 200 driven in a Peltiermode or a heater mode to adjust the temperature of the wafer 109 to apredetermined value, when a value of the high-frequency power for thebias formation is relatively large, and the target temperature of thetemperature adjustment array 200 and the heat input amount or themagnitude of the high-frequency power are in an inversely proportionalrelation.

In addition, the correlation coefficient changes depending on the kindof the process gas, the internal pressure of the processing chamber 104,and the material of the member configuring the sample stage 115. Aninfluence of the kind, the internal pressure, and the material isrepresented by a coefficient Z and the target temperature of the k-thtemperature adjustment array 200 is detected on the basis of thefollowing formula, in the control device according to this embodiment.

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack & \; \\{{Tk} = {\sum\limits_{n - 1}^{n = h}{\left( {\lambda\; k\; n \times {Twn}} \right) \div \left( {K \times {RF}} \right)}}} & \left( {{formula}\mspace{14mu} 1} \right)\end{matrix}$Tn: control temperature (sensor feedback temperature) of n-th elementTwn: temperature of wafer on n-th elementΛkn: influence constant from n-th element to k-th elementK: proportional constantRF: bias power

In this example, each coefficient of the formula (1) is detectedpreviously by experiments, is stored in a storage device such as a RAMand a ROM in the control device, and is set. In the control device, thetarget temperature of each of the first to h-th temperature adjustmentarrays 200 is detected using a value of each coefficient duringprocessing of the wafer 109. In this configuration, the temperature ofthe wafer 109 is not predicted by an observer. As in this example, eventhough the operation of the temperature adjustment arrays 200 of thesame number disposed in each of multiple places is adjusted to adjustthe temperatures of the multiple places, responsiveness of theadjustment can be sufficiently raised and a practical application isenabled.

An example of the operation of the temperature adjustment arraysaccording to this embodiment will be described using FIG. 6. FIG. 6 is adiagram schematically illustrating the operation of the temperatureadjustment arrays of the sample stage according to the embodimentillustrated in FIG. 2.

In FIG. 6, each of temperature adjustment arrays 400 and 401 has thesame configuration as the configuration of the temperature adjustmentarray 200 illustrated in FIG. 2. Each of the temperature adjustmentarrays 400 and 401 is electrically connected in series to the constantcurrent power supply 207 via the positive and negative terminalelectrodes of the polarity switch 208, each temperature adjustment arrayhas the bypass relay 206 connected to a path supplying power in parallelto each temperature adjustment array, and an element of each temperatureadjustment array is operated in the heater mode.

When a temperature detected from a signal detected by the temperaturesensor of the temperature adjustment array 401 is higher than the targettemperature detected by the mechanism illustrated in FIG. 5, it isnecessary to decrease a current supplied to the temperature adjustmentarray 400 or stop the temperature adjustment array 400 and decrease anamount of heat to be generated. For this reason, the bypass relay 206connected in parallel to the temperature adjustment array 400 is turnedon to bypass the current supplied to the temperature adjustment array400 according to a command signal from the control device. When thetemperature monitored by the temperature adjustment array 401 is lowerthan the target temperature, the bypass relay 206 is turned off tosupply the current to the temperature adjustment array 400. An ON or OFFperiod of the bypass relay 206 is set to be proportional to a differencebetween the temperature detected by the control device from an outputreceived from the temperature sensor 218 and the target temperature, tobe proportional to an integral value of the difference, and to beproportional to a differential value of the difference, using thedifference.

A process for detecting the target temperature from a distribution ofdetected CD values will be described using FIG. 7. FIG. 7 is a flowchartillustrating a process for detecting a target temperature of eachtemperature adjustment array by the control device in the plasmaprocessing device according to the embodiment illustrated in FIG. 1.

In FIG. 7, before processing the wafer 109 to manufacture asemiconductor device as a product, the temperatures of all of thetemperature adjustment arrays 200 are adjusted to become a predeterminedfirst temperature, a wafer 109 for a test having the same configurationas the configuration of the wafer 109 for the product and having thesame film structure as the film structure of the wafer 109 for theproduct on a top surface is pressed under the same process conditions(so-called recipe) such as a pressure of the processing chamber 104, acomposition of the process gas, and a flow rate, a shape of a surface ofthe wafer 109 for the test is measured, and a CD average value 1 isdetected (step 701). Next, the temperature of the temperature adjustmentarray 200 is adjusted to become a second temperature different from thefirst temperature, a wafer 109 for a different test is processed, ashape of a surface of the wafer 109 for the different test is measured,and a CD average value 2 is detected (step 702).

Next, a correlation of a difference of the CD average value 1 and the CDaverage value 2 and a difference of the first and second temperatures isdetected and a temperature correlation coefficient of the CD values isdetected (step 703). The target temperature of each temperatureadjustment array 200 corresponding to the CD value measured using thetemperature correlation coefficient or used as a specification of aprocessing shape is calculated (step 704). A calculated temperaturevalue is set as the target temperature and the wafer 109 for the productis processed (step 705).

For example, a graphical user interface (GUI) may be displayed on adisplay unit of a display device such as a CRT and a liquid crystalmonitor connected to the plasma processing device 100, such that a userinputs the CD measurement value 1 and the first temperature and the CDmeasurement value 2 and the second temperature using the GUI, and theplasma processing device 100 may be operated by the control device, onthe basis of the input values. The control device executes PWM controlon the bypass relay 206, on the basis of the value of the targettemperature received via a communication interface connected to acommunication unit not illustrated in the drawings. In addition, anarithmetic unit such as a microprocessor made of a semiconductor in thecontrol device reads software describing an algorithm to adjust anoperation of each temperature adjustment array 200 according to thereceived value of the target temperature and the value of thetemperature detected from the signal output from the temperature sensor218 from a storage device such as a RAM, a ROM, and a hard disk wherethe software is previously stored and calculates a command signal forcontrol.

A calibration method of the plurality of temperature sensors 218 isdescribed. Because the temperature sensors 218 are degraded over time, atemperature of a surface of the sample stage 115 close to a positionwhere a temperature monitor is disposed at a cooling medium temperatureof 220° C. may be detected and the value of the temperature detectedfrom the temperature sensor 218 may be calibrated. A standardtemperature sensor used for the calibration may be a wafer-type sensoror a contact-type thermometer and any temperature measurement devicethat is already calibrated at the time of measurement may be used. Inthis embodiment, the temperature sensor is a thermister. However, a PTsensor, a thermocouple, and a fluorescent thermometer may be used.

In addition, in this embodiment, a silicon oxide film is set as thematerial of the etching process target and methane tetrafluoride gas,oxygen gas, and methane trifluoride gas are used as the etching gas andthe cleaning gas. However, the same effect is obtained even when notonly the silicon oxide film but also a polysilicon film, a photoresistfilm, an organic antireflection film, an inorganic antireflection film,an organic material, an inorganic material, a silicon oxide film, asilicon nitride oxide film, a silicon nitride film, a Low-k material, aHigh-k material, an amorphous carbon film, a Si substrate, and a metalmaterial are set as the material of the etching process target. Inaddition, chlorine gas, hydrogen bromide gas, methane tetrafluoride gas,methane trifluoride, difluoride methane, argon gas, helium gas, oxygengas, nitrogen gas, carbon dioxide, carbon monoxide, hydrogen, ammonia,octafluoro propane, nitrogen trifluoride, sulfur hexafluoride gas,methane gas, silicon tetrafluoride gas, silicon tetrachloride gas, neongas, krypton gas, xenon gas, and radon gas can be used as the etchinggas.

In the embodiment described above, the etching device using themicrowave ECR discharge has been described. However, the same functionand effect can be obtained even in a dry etching device using other typeof discharge (effective magnetic field UHF discharge,capacitance-coupled discharge, induction-coupled discharge, magnetrondischarge, surface-wave excitation discharge, and transfer-coupleddischarge). In addition, in the embodiment described above, the etchingdevice has been described. However, the same function and effect can beobtained even in other type of a plasma processing device to performplasma processing, for example, a plasma CVD device, an asking device,and a surface modification device.

What is claimed is:
 1. A plasma processing apparatus that includes aprocessing chamber which is disposed in a vacuum vessel and isdecompressed internally and a plasma is generated using process gassupplied therein, and a sample stage which is disposed in the processingchamber and on which a sample of a process target is disposed and held,the sample being processed using the plasma, the plasma processingapparatus comprising: a dielectric film which is disposed on a metallicbase which configure the sample stage, the dielectric film including aconductive film disposed internally therein; a first power supplyconfigured to supply high-frequency power to the conductive film; atleast one aggregation of a plurality of Peltier elements which arehoused inside a space in the base and connected in series, each of theplurality of Peltier elements being configured to have both heatgenerating and cooling functions, and being equipped in contact with aceiling of the space and separated from the conductive film by the baseand the dielectric film; and one or more second power supplies, each ofthe one or more second power supplies being connected to each of the atleast one aggregation of the plurality of Peltier elements via apolarity switch and being configured to supply electric power to drivethe plurality of Peltier elements to have either of the heat generationor cooling functions; and a plurality of current bypass relays, each ofwhich are connected in parallel to the plurality of Peltier elements ineach of the at least one aggregation, each of the current bypass relaysbeing configured to adjust amounts of current of the electric powerprovided from the one or more second power supplies, wherein the basesurrounds the Peltier elements and the base is connected to groundpotential.
 2. The plasma processing apparatus according to claim 1,wherein: a filter to suppress the high-frequency power from the firstpower supply is not provided on the feeding path of the second powersupply to the Peltier elements, and the plurality of Peltier elementsconfiguring the aggregation are disposed in a circumferential directionof the sample, and are supplied with the electric power.
 3. The plasmaprocessing apparatus according to claim 2, wherein: the plurality ofPeltier elements configuring the aggregation are disposed in aconcentric shape in a circumferential direction at a plurality of radialpositions of the sample.
 4. The plasma processing apparatus according toclaim 1, wherein: the plurality of Peltier elements are configured toexecute heating and cooling operations.
 5. The plasma processingapparatus according to claim 1, further comprising: a cooling mediumflow channel through which a cooling medium circulates, the coolingmedium flow channel disposed below the plurality of Peltier elements inthe base and adjusting a temperature of the base.
 6. The plasmaprocessing apparatus according to claim 5, wherein: the cooling mediumis water, ethylene glycol, or an insulating cooling medium.
 7. Theplasma processing apparatus according to claim 1, further comprising: aplurality of elastic heat insulating placement stages which are housedinside the space in the base, each of the elastic heat insulatingplacement stages being equipped in contact with a floor of the space,wherein the Peltier elements are disposed on the elastic heat insulatingplacement stages and held in contact with the ceiling of the space bythe elastic heat insulating placement stages.
 8. The plasma processingapparatus according to claim 1, wherein: each of the plurality of bypassrelays are configured to switch one period in which a smaller current ofthe electric power is provided and another period in which a largercurrent of the electric power is provided to each of the plurality ofPeltier elements connected in parallel.